[PATCH 2/2] loop: Test to detect a race condition between loop detach and open

Gulam Mohamed
2024-05-21T22:42:55Z

When one process opens a loop device partition and another process detaches
it, there will be a race condition due to which stale loop partitions are
created causing IO errors. This test will detect the race

Signed-off-by: Gulam Mohamed <gulam.mohamed@oracle.com>
---
tests/loop/010 | 90 ++++++++++++++++++++++++++++++++++++++++++++++
tests/loop/010.out | 2 ++
2 files changed, 92 insertions(+)
create mode 100755 tests/loop/010
create mode 100644 tests/loop/010.out

diff --git a/tests/loop/010 b/tests/loop/010
new file mode 100755
index 000000000000..ea93a120d51a
--- /dev/null
+++ b/tests/loop/010
@@ -0,0 +1,90 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2024, Oracle and/or its affiliates.
+#
+# Test to detect a race between loop detach and loop open which creates
+# stale loop partitions when one process opens the loop partition and
+# another process detaches the loop device
+#
+. tests/loop/rc
+DESCRIPTION="check stale loop partition"
+TIMED=1
+
+requires() {
+ _have_program parted
+ _have_program mkfs.xfs
+}
+
+image_file="/tmp/loopImg"
+line1="partition scan of loop0 failed (rc=-16)"
+
+function create_loop()
+{
+ while [ 1 ]
+ do
+ loop_device="$(losetup -P -f --show "${image_file}")"
+ blkid /dev/loop0p1 >> /dev/null 2>&1
+ done
+}
+
+function detach_loop()
+{
+ while [ 1 ]
+ do
+ if [ -e /dev/loop0 ]; then
+ losetup -d /dev/loop0 > /dev/null 2>&1
+ fi
+ done
+}
+
+test() {
+ echo "Running ${TEST_NAME}"
+ local failure="/tmp/failure"
+ touch $failure
+ echo 0 > $failure
+ dmesg -c > /dev/null 2>&1
+
+ truncate -s 2G "${image_file}"
+ parted -a none -s "${image_file}" mklabel gpt
+ loop_device="$(losetup -P -f --show "${image_file}")"
+ parted -a none -s "${loop_device}" mkpart primary 64s 109051s
+
+ udevadm settle
+ if [ ! -e "${loop_device}" ]; then
+ return 1
+ fi
+
+ mkfs.xfs -f "${loop_device}p1" > /dev/null 2>&1
+
+ losetup -d "${loop_device}" > /dev/null 2>&1
+
+ create_loop &
+ create_pid=$!
+ detach_loop &
+ detach_pid=$!
+
+ sleep "${TIMEOUT:-180}"
+ {
+ kill -9 $create_pid
+ kill -9 $detach_pid
+ wait
+ sleep 1
+ } 2>/dev/null
+
+ losetup -D > /dev/null 2>&1
+ dmesg | while IFS= read -r line2
+ do
+ match=$(echo "$line2" | grep -o "$line1")
+ if [ "$line1" == "$match" ]; then
+ echo 1 > "/tmp/failure"
+ break
+ fi
+ done
+ failed=$(cat $failure)
+ if [ $failed -eq 0 ]; then
+ echo "Test complete"
+ else
+ echo "Test failed"
+ fi
+ rm -f $failure
+}
diff --git a/tests/loop/010.out b/tests/loop/010.out
new file mode 100644
index 000000000000..64a6aee00b8a
--- /dev/null
+++ b/tests/loop/010.out
@@ -0,0 +1,2 @@
+Running loop/010
+Test complete
--
2.39.3